A. Field of the Invention
This invention relates to a method employing an additive for preventing caking of a body of granular sodium chloride at temperatures between about 400.degree. C and the melting point of sodium chloride.
B. Description of the Prior Art
It is known in the art to dispose of organic waste contained in aqueous effluent streams also containing inorganic solids, by incineration in or over a bed of fluidized granular material, i.e., wherein the granular material is maintained in a state of turbulent suspension in a hot, upflowing gas. See, for example, Copeland et al, U.S. Pat. No. 3,309,262; Albertson et al., U.S. Pat. No. 3,319,586; and Mallat et al., "Incinerate Sludge and Caustic," Hydrocarbon Processing, pp. 121-122, May, 1970. In such processes, the waste stream to be disposed of is customarily sprayed into the fluidized bed itself or into the so-called freeboard zone above the bed. Upon contact with the bed, the organics are oxidized and are vented to the atmosphere, and the solid inorganics become part of the bed itself. The accumulated inorganics can be recovered from the reactor and profitably recycled by withdrawing portions of the bed during the incineration process.
It is a frequent practice to employ an inert material, such as sand, during start-up of such incineration processes. As the process is carried out and portions of the bed removed as the inorganics accumulate, it is apparent that the sand will be gradually replaced by the inorganic components of the waste stream. Until such time as the replacement is substantially complete, however, the portions of the bed extracted will contain a substantial amount of the start-up bed material, and may be unsuitable for further use without additional treatment. In order to avoid any waste of the inorganics recovered from the waste stream shortly after startup, therefore, it would be most advantageous to be able to employ as a bed material during start-up, a material having a composition similar to the inorganics contained in the waste stream.
In attempting to bring a bed consisting substantially of sodium chloride up to temperatures on the order of about 650.degree. C, caking, i.e., agglomeration of the salt particles, was encountered. Depending on various factors such as particles size and shape, velocity of the fluidizing gas, and the like, the evidence of caking was first encountered at various temperatures ranging from about 400.degree. C to somewhat less than about 600.degree. C.
It is known in the art to employ various freeflowing agents for salt. See, for example, Kaufman, Sodium Chloride--The Production and Properties of Salt and Brine, pp. 275-276, Reinhold Publishing Corp., New York, 1960. The prior art, however, has taught use of such free-flowing agents only to inhibit caking at more or less ambient temperatures, e.g., from about -35.degree. to about 55.degree. C. Caking at such temperatures is well known to be caused principally by water vapor.